Method for deodorizing o,o-dialkyl s-(alkylthio)alkyl phosphorodithioates



United States Patent US. Cl. 260-989 1 Claim ABSTRACT OF THE DISCLOSURE A method for deodorizing mercaptan-containing, organic dithiophosphates. The organic dithiophosphates are pesticides.

This invention relates to an improved process for deodorizing malodorous mercaptan-containing, organic dithiophosphate compositions. More particularly, the invention is concerned with an improved process for eliminating offensive odors from and stabilizing the same in dithiophosphate pesticides having the formula:

wherein R and R each represents the same or different alkyl substituent containing from 1 to 4 carbon .atoms and R stands for a lower alkylene bridge.

Several attractive processes for the effective removal of objectionable odors from certain of the thiophosphate pesticides have been developed in the recent past. Unfortunately, not all such processes are effective for the treatment of all thiophosphates. For instance, an ozonization process for reducing objectionable odors of dithiophosphates as disclosed in United States Letters Patent No. 2,980,723, issued on Apr. 18, 1961, is not wholly satisfactory for treatment of 0,0-dialkyl S-(alkylthio) alkyl dithiophosphates. This is because ozonization appears to cause rapid degradation of such dithiophosphates. Another known procedure for effecting the deodorization of dialkyl thiophosphates of a mercaptosuccinate which involves treatment with an organic copper complex is disclosed in British Patent No. 960,013. The latter teaches that if deodorization is to be effective the presence of an oxygen donor is required. The donor may be incorporated into the pesticides either as atmospheric oxygen or as a ketonic peroxide, such as dimethyl ketone peroxide or methyl ethyl ketone peroxide. Further, other pesticides, such as diethyl p-chlorophenylthiomethyl dithiophosphate and diethyl p-nitrophenol thiophosphate can be similarly treated by the British procedure. However, when the process of the British patent is applied to pesticidal dithiophosphates of the formula:

wherein R, R and R are as defined hereina-bove, the process does not provide a wholly satisfactory method for deodorizing such compounds, since strong oxidizing agents tend to degrade them.

It is, therefore, a principal object of the invention to provide a process for effecting removal of objectionable odors from 0,0-dialkyl S (alkylthi0)alkyl dithiophosphates. It is also an object of the invention to provide a process for stabilizing the latter odorwise over a prolonged period of time. Other objects and advantages will become apparent from a consideration of the following description.

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To this end, it has been found that these objects can be unexpectedly attained by providing for a series of critical operations, thereby overcoming degradation and instability. These involve the practice of three essential steps which comprise:

(1) Treating an 0,0-dialkyl S-(alkylthio)alkyl dithiophosphate with between about 1.5% and 4.0% by weight of either an organic or inorganic peroxide or an organic or inorganic hydroperoxide;

(2) Heating the mixture of a temperature between about C. and 90 C., usually for from about 15 minutes to about 20 hours and, preferably, from about 20 minutes to about 45 minutes; and

(3) Admixing with the treated mixture between about 0.75% and 5% by weight of an aliphatic or aromatic aldehyde.

Failure to observe the foregoing sequential operations does not result in enhanced deodorization and stabilization of certain dithiophosphates.

Exemplary dithiophosphates which may be deodorized by treatment in accordance with the invention are: 0,0- diethyl S-(ethylthio) methyl phosphorodithioate, 0,0-dimethyl S-(ethylthio) methyl phosphorodithioate, 0,0-dimethyl S-Z-(ethylthio) ethyl phosphorodithioate, 0,0-diethyl S-(ethylthio) ethyl phosphorodithioate.

Illustrative of the organic or organic peroxides and hydroperoxides useful in the process of the invention are: cumene hydroperoxide, cumene peroxide, hydrogen peroxide, benzol peroxide, t-butyl hydroperoxide, potassium peroxide, pinene hydroperoxide and the like, of which cumene hydroperoxide is preferred.

As illustrative of aldehydes amenable to use in the process of the invention are: methylprotocatechuic aldehyde, ethylprotocatechuic aldehyde, ethyl glyoxylate, benzaldehyde and salicylaldehyde. The preferred aldehyde is methylprotocatechuic aldehyde.

For optimum results, the malodorous dithiophosphate is treated with sufficient organic or inorganic peroxide or hydroperoxide to react with all of the odor producing impurities present therein. In general, from about 1.75% to 3% by weight of the peroxide of hydroperoxide is adequate for this treatment. Subsequent to peroxide or hydroperoxide addition, the mixture is heated, preferably, to about C. to C. for between about 30 and 45 minutes. The mixture is then treated with between about 0.75 and 3% by weight of the aldehyde, preferably methylprotocatechuic aldehyde. The aldehyde treatment is preferably carried out at a temperature between about 50 C. and 85 C.

The following examples will further illustrate the criticality of the sequential steps set forth above. Unless otherwise stated, the percentages are by weight.

EXAMPLE 1 To det mine the various effects of the deodorizing and stabili ation treatments on technical grade, 0,0- diethyl S-(ethylthio) methyl photophorodithioate, hereinafter known as T.G., five separate samples of T.G. are subjected to the following comparative procedures:

( 1) T.G. is admixed with 3% cumene hydroperoxide and the mixture heated to C. for 30 minutes;

T.G. and 0.5% of 2,4-pentanedione copper complex are admixed at room temperature. Resulting mixture is then treated with 1% of methyl ethyl ketone peroxide; and

(6) T.G., untreated, as the control sample.

The treated T.G. as well as the untreated T.G. are each sprayed individually on 24/48 mesh granular attapulgite previously treated with 4% of diethylene glycol as a deactivator. The individual preparations are thoroughly mixed to assure uniform distribution of the toxicant on the particles. The formulations are then placed in sealed containers and stored at room temperature for twelve weeks.

After storage, the T.G. samples are evaluated by the known Schefi'es method of paired comparisons. Sixty judges are employed and each sample is compared with every other sample in the test. To eliminate a possible bias due to the desensitization of the olfactory nerves by the first sample proffered, thereby causing a preference for the second, both orders of presentation for each sample pair are obtained for evaluation.

In order to determine the relative preference of N samples, each sample is compared with each of the other (N-l) samples, with both orders of presentation for each pair of samples, the number of permutations for N samples two at active, is therefore N(N-1). Preferences are scored on an arbitary numerical scale, 12 for a high performance, 2 for a strong rejection and 0 for no preference. If preference is not strong, the samples are scored :1. The sign of the score depends upon wherether the preference is for the first or second sample proffered. The preferred sample received a positive score when it is proffered first and a negative score when proffered second. In the absence of a desensitization effect, and random or systematic error, the sum of the scores for both orders of presentation for each sample pair would be zero.

A scoring box is made up with the row scores pertaining to the preference of samples proffered first and column scores pertaining to the preference of samples proffered second. The total score for each sample is obtreated in accordance with the invention is rated vastly superior odorwise to all other treatments.

Total number of treatments compared: m=6.

Total number of judges for each pair; 2r=4 (r judges for each order of permutation).

Total number of permutations: 2M=m(ml) =30. Highest possible an valuc=+1.667. =Rejected (mean average of preference judged against all samples). +=Accepted.

EXAMPLE 2 In the following tests separate samples of 0,0-diethyl S-(ethylthio) methyl phosphorodithioate are treated in the manner described in Example 1, except that the prepared samples are stored as liquids rather than being applied to a granular solid. The treated samples are placed in sealed containers and stored at room temperature for one month. They are then presented to judges for the odor preference and evaluated by the Schelfes method of paired comparisons. The data obtained are provided in Table II below. Clearly, a strong preference for the sample prepared by the process of the invention is shown.

The data also show a need for a treatment which provides sustained odor control. It can be seen, however, that initial treatment with 3% cumene hydroperoxide produces good odor control, but that after one month storage, the odor control achieved by the process of the invention is found to be substantially better.

TABLE II Type of Formulation Main Efiect One Type of Treatment Evaluated Parameter month,

as Initial 25 C.

3% cumene hydroperoxide, 30 mins. 0,0-diethyl S-(ethylthio) l-l. 042 +0. 792

at 90 0. methyl phosphorodithioa e. 1% methylprotocatechuic aldehyde, .....d0 0. 292 0. 292

slalom tempeil'iatgrre. id +17 cumene y operox e :uethylprotocatechuic aldehyde,]"" +1350! 30 mins. at 90 C. 1% ozonized diethylmaleate, room ...-do 0.042 0.209

temperature. 0.5% 2, -pentanedione copper complex-[4% methyl ethyl d0 0. 416 0. 508 ketone peroxide, room temperature. Control (untreated technical ma- .--do 1. 083 1. 041

terial).

Total number of treatments compared: m= 6.

Total number of judges for each pair: 2r=4 (r judges for each order of permutation). Total number of permutations: 2M=m(m1)=30. Highest possible as value=+1.667. "Main effect parameters calculated from tests using emulsifiable concentrate 47.5% of some toxicant, 39% xylene and 10% of an emulsifier showed the same general magnitude.

Denotes significant odor improvement.

EXAMPLE 3 In the following tests separate samples of 0,0-diethyl S-(ethylthio) methyl phosphorodithioate are treated with 1%, 1.5%, 2.0% or 3.0% by weight of cumene hydroperoxide. These samples are heated to C. or C. for 30 minutes and cooled to between 60 C. and 80 C. and 1% by weight of methylprotocatechuic aldehyde is added to each sample treated. Separate portions of of xylene and 10% by weight of a mixture of an alkyl attapulgite granular 24/48 mesh are then treated with aryl polyether alcohol and a calcium alkyl aryl sulfonate. 10% by weight of toxicant from the above preparations Two milliliters of each formulation are mixed with 98 and the thus prepared granulars placed in individual mililiters of water and the thus prepared samples are sealed containers for storage and evaluation. Portions of 5 evaluated by Scheites method of paired comparisons and each of the prepared materials are also stored as liquids the results are provided in Table IV below. The data in separate sealed containers, After one month storage clearly establishes the necessity of heating the peroxide at room temperature, all preparations are evaluated by treated toxicant to a temperature above 60 C.

TABLE IV Treatment Time Tempera- Type of Formulation Tested Main Effect ture, 0. Parameter as Control 30 mins- 90 0,0-diethyl S-(ethylthio) methyl 0. 833

phosphorodithioate (emulsifiable concentrate). 3% CHP 16 hours..- 60 do 0. 167 3% CHP- 30 ruins... 90 -do -l--1.000

the Scheffes method of paired comparisons. The results EXAMPLE 5 provided in the table below establish the lowest eifective concentration of peroxide at the 1.5% level of the To determine the effect of peroxide concentration in dithiophosphate treated. 25 treatment of dithiophosphates, replicate samples of 0,0-

TABLE III Treatment Methylproto- Reaction, Temp- Type of Formulation Tested Main Eflect CHP+ catechuic aldeerature and Time Parameter on Level, Perhyde Level, Percent cent 3 1 min./90 O Attapulgite granular 24/48 mesh +10% +0.2500

w./w. toxicant. 2 1 30 min/80 0-. n +0 2500 1. 5 1 30 min./80 C "do +0.1250 1. 0 1 30 mi11./80 0 "do -0. 0250 3 1 30 min-[90 C..- Technical 0,0-diethyl S-(ethylthio) +0. 2500 methyl phosphorodithioate. 2 1 30 min/80 C- on +0.3750 1. 5 1 30 min/80 0 do 0. 0000 1. 1 a0 min/80 C "do.-. -o. 6250 Total number of treatments: m=4.

Total number of judges for each air: 2r=4 (2 judges for each order of permutation). Total number of permutations: 21 =m(m-1) =12. Highest possible an value =+1. 5000.

+CHP= Cumene hydroperoxide.

EXAMPLE 4 diethyl S-(ethylthio) methyl phosphorodithioate emulsi- To determine the eifect of time and temperature on fiable concentrate treated with 2% or 3% the process of the instant invention, separate samples of cumene hydroperoxlde and heated to 90 for 3 technical 0,0-diethyl S-(ethylthio) methyl phosphorodi- The Samples a thfan formulated as emiflslfiable thioate are (1) heated to C. for 30 minutes; (2) concentrates as described in Example 4, placed in sealed treated with 3% by weight of cumene hydroperoxide and containers and stored at room temperature for one month, heated to for 16 hours; (3) treated with 3% then evaluated In accordance with Scheifes method of cumene .hydropemxide and heated to for 30 pa1red comparisons. The results which appear in Table V utes. These samples are then formulated as emulsifiable below Y indicate the need for treatment Of the concentrates containing 48% by weight of 0,0-diethyl dithiophosphate with more than about 1% by weight of S-(ethylthio) methyl phosphorodithioate, 39% by weight 55 the peroxide.

TABLE V Main Efiect Rephcates GHP Level Treatment Type of Formulation Tested Parameter a4 A B l 0,0-diethyl S-(ethylthio) methyl +0. 187 1% CHP 90 0.]30 m1n phosphorodithioate (emulsifiable --0.062 +0.042

concentrate). +0. 000 +0. 312 2% CHP 90 C./30min -do +0. 312 +0. 313

+0.438 +0. 025 3% CHP 90 C./30 mm .do +0688 +0604 +0. 375 -1. Control untreated do -0. 928 0. 958

1 Average for 3 replicates. Total number of treatments compared: 3m=12(m=4).

Total number of judges: 3X2r=12 (6 for each order of permutation). Total number of permutations: 3X2M=m(m1) =36. Highest possible a; va1ue=+1.500. "2 ml. 0,0-diethyl S-(ethylthio) methyl phosphorodithioate emulsifiable concentrate-{-98 ml. tap water. A=a values for each treatment series (each material judged by 4 difierent judges). B =1: values cumulative for all treatments (each material judged by 12 difierent judges). CHP= Cumene hydroperoxide.

7 EXAMPLE 6 0,0-diethyl S-(ethylthio) methyl phosphorodithioate is treated with 3%, by weight, of cumene hydroperoxide, then heated to 90 C. for 30 minutes, and cooled to 60 C. Separate samples from the so-treated phosphorodithioate are treated with 0.50%, 0.75% or 1.0%, by weight, of methylprotocatechuic aldehyde. Twelve percent, by weight, of each preparation is sprayed on individual samples of 24/48 mesh granular attapulgite, which has been previously deactivated with 4% of diethylene glycol. The formulations are then stored at room temperature for one month and evaluated by Schelfes method of paired comparisons. The results in Table VI below clearly establish the need for addition of about 1% by Weight of the aldehyde to the peroxide treated toxicant.

Total number of treatments; m=4.

Total number of judges for each pair: 2r=4 (2 judges in each order of permutations) Total number or permutations: 2M=m(m-1) =12. Highest possible a value=+1.500. CHP= Cumene hydroperoxide.

EXAMPLE 7 Following the procedures employed in Example 4 for sample preparation and evaluation but altering the heating temperature to 7 C., 80 C. and 90 C. and limiting the heating period to 20 minutes, there is established in three samples the desirability of heating the treated toxicant to at least about 80 C. for 20 minutes. The results are tabularized in Table VII below.

TABLE VII Treat- Time, Temper- Tested As- Main Effect ment mins. ature, Parameter aa degrees 3% CHP 20 0,0diethyl S-(eth- 0.667

ylthio) methyl phosphorodithioate 3% CHP 20 d +0.167 3% CHP 20 +0. 500

*Total number of treatments compared: m=3.

Total number of judges for each pair: 2r=4 (r=2 for each order of permutation).

Total number of permutations 2M=m(m- 1) =6. Highest possible or: value =+1.333. Denotes significant odor improvement. Denotes that this treatment is significantly worse than the two other samples.

CHP= Cumeue hydroperoxide.

We claim: 1. A method for removing objectionable odors from 0,0-diethyl S-(ethylthio) methyl phosphorodithioate OHARLES B. PARKER, Primary Examiner.

A. H. SUTTO, Assistant Examiner.

U.S. Cl. X.R. 

